Global Position System (GPS) has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, and scientific uses, providing that it enables a GPS receiver to rapidly and effectively determine its location, speed and direction at high accuracy. However, as GPS signals can be easily affected by environmental factors, such as terrain and weather, the signal delay effect resulting from such environment factors may severely affect the GPS position accuracy, which is especially critical for locations where the GPS signals are reflected off or even blocked by surrounding terrain, buildings, canyon walls, or indoors, etc. For achieving accurately positioning an object without being affected by shields, other positioning apparatuses for assisting the GPS are required.
One such positioning apparatus is disclosed in U.S. Pat. No. 6,944,542, entitled “Position Determination System for Movable Objects or Personnel”, which is a position determination system integrated with a GPS receiver, an INS (inertial navigation system) device and a wireless transmission module an inertial navigation system (INS). While the aforesaid positioning determination system is used for tracking a movable object, an initial position of the movable object is first being located by the GPS receiver to be used as the datum point of the INS device, with reference to which, when the movable object is moved to a location where the GPS signal is blocked and thus the GPS receiver is no longer able to locate the position of the movable object, the velocity/acceleration data indicative of velocity/acceleration of the movable object detected by the INS device can be converted into meaningful position signals that is to be transmitted to a monitor station for tracking the movement of the object. For instance, miners inside mines could benefit from such a position determination system, in that the position of a miner could first be uniquely determined and located by the GPS receiver, and then as soon as the miner enters the mine where the GPS signal is blocked, the position determination system will switch to locate the position of the miner by the INS device while transmitting the detected position to a ground monitoring station by the wireless transmission module. However, the aforesaid position determination system is only a local positioning system that it is incapable of positioning, tracking and monitoring a movable object in a remote manner.